Recirculating aquaculture systems (RAS) claim to offer better welfare control than sea cages, but the welfare outcomes depend critically on design, management, and species suitability.
RAS technology offers genuine welfare improvements over sea cage aquaculture in some dimensions: elimination of sea lice, avoidance of extreme weather exposure, and precise control of water quality. But the controlled environment advantage is only realised when systems are well-designed and well-managed. The commercial pressure to pack as many fish as possible into expensive infrastructure creates a structural tendency toward overstocking that compromises welfare. Additionally, the enclosed, stimulus-poor environment of a RAS tank may be less suitable for some species than the variable, enriched environment of sea cages. Species-specific welfare evaluation of RAS performance — rather than assuming the technology is inherently more welfare-positive than alternatives — is essential for honest assessment.